A method for cleaning the surface of invar strip

Abstract

A method for cleaning the surface of INVAR strip includes the following steps: S1, cleaning the surface of INVAR strip with surface conditioning liquid; S2, treating the surface of INVAR strip cleaned in step S1 with pickling section; S3, treating the surface of INVAR strip treated in step S2 with alkaline cleaning section; S4, treating the surface of INVAR strip cleaned in step S3 with water cleaning section and drying section. The method can improve the cleaning effect and the rust prevention ability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cleaning methods, in particular to a method for cleaning the surface of INVAR strip. BACKGROUND

[0002] In the prior art, for the removal of foreign matter on the surface of INVAR strip, a continuous cleaning process based on "degreasing, pickling, water washing, and air knife drying" has been disclosed. However, the removal efficiency of foreign matter on the surface of INVAR strip in the existing process is limited. In addition, after the existing process, there are macroscopic white spot defects on the surface of the strip, which are caused by the non-dense and uneven thickness of the original oxide film on the surface of INVAR. If acid pickling is directly used, the acid solution will preferentially penetrate the weak areas of the oxide film, causing local over-corrosion and forming pitting, which appears as white spots under subsequent reflected light, seriously affecting the surface appearance of INVAR strip and the quality of subsequent precision processing such as plating and etching.

[0003] Only water washing and air knife blowing and drying are provided after the pickling section, and acid solution residues occasionally occur. INVAR alloy is sensitive to acid solution, and acid solution residues can induce secondary corrosion during subsequent storage and heat treatment, resulting in rust spots on the surface and reducing the corrosion resistance of the material.

[0004] In addition, the existing process lacks effective passivation treatment, and the surface of INVAR strip is highly active after water washing, which is easily rusted when exposed to a humid environment.

[0005] In view of the above defects, the prior art adds an alkali neutralization step after pickling, but does not optimize the composition, concentration and spraying process of the alkali solution, resulting in incomplete neutralization. Therefore, there is an urgent need for an INVAR strip surface cleaning method with high cleanliness, low defect rate and strong rust prevention ability. SUMMARY

[0006] The purpose of the present application is to provide an INVAR strip surface cleaning method that can improve the removal efficiency of foreign matter on the surface of INVAR strip, has a low defect rate and strong rust prevention ability.

[0007] A method for cleaning the surface of INVAR strip, comprising the steps of: S1, first cleaning the surface of INVAR strip with a surface conditioning liquid; S2, treating the surface of INVAR strip cleaned in step S1 with an acid pickling section; S3, treating the surface of INVAR strip treated in step S2 with an alkali pickling section; and S4, treating the surface of INVAR strip cleaned in step S3 with a water washing section and a drying section.

[0008] Further, the surface conditioning liquid comprises a surfactant, an acidic component, a corrosion inhibitor, deionized water, the surfactant is sodium dodecyl sulfonate, the acidic component is composed of sulfamoyl acid, phosphoric acid and potassium acetate, and the corrosion inhibitor is benzotriazole.

[0009] Further, the ratio of the surfactant to the acidic component is 1:1.5-1:2.0, and the molar ratio of the surfactant to the corrosion inhibitor is 1:0.5-1:0.8.

[0010] Further, the sulfamoyl acid accounts for 35-45% of the total amount of the acidic component, the potassium acetate accounts for 15-25% of the total amount of the acidic component, and the compounding ratio of the phosphoric acid to the sulfamoyl acid is 1:1.2-1:1.5.

[0011] Further, the concentration of the sodium dodecyl sulfonate is 6-8%, the concentration of the sulfamoyl acid is 4-6%, the concentration of the phosphoric acid is 3-5%, the concentration of the potassium acetate is 2-4%, and the concentration of the benzotriazole is 0.8-1.2%.

[0012] Further, the pickling section is composed of three-stage pickling, the first-stage pickling is composed of 5-8% glycolic acid and 0.5-1% sodium gluconate, the second-stage pickling is composed of 1.5-2.5% sulfamic acid and 0.1-0.5% polyaspartic acid, and the third-stage pickling is composed of 0.8-1.8% ammonium oxalate and 0.02-0.05% fluorocarbon surfactant.

[0013] Further, the spraying pressure of the first-stage pickling is 0.2-0.3 bar, the spraying angle is 15-20° along the strip material direction, the spraying height is 250-300 mm, the temperature is 35-45℃, and the process time is 90-110 s; the spraying pressure of the second-stage pickling is 0.8-1.0 bar, the spraying angle is 60-75° along the reverse strip material direction, the spraying height is 100-150 mm, the temperature is 40-50℃, and the process time is 60-80 s; the spraying pressure of the third-stage pickling is 0.1-0.2 bar, the spraying angle is 5-10° along the strip material direction, the spraying height is 300-350 mm, the temperature is 30-40℃, and the process time is 45-55 s.

[0014] Furthermore, the alkaline washing section consists of two alkaline washing sections; the first alkaline washing section has a spray pressure of 1.8-2.2 bar, a spray angle of 60°-70° along the opposite direction of the strip, and a spray height of 80mm-90mm; the second alkaline washing section has a spray pressure of 0.8-1.0 bar, a spray angle of 30°-40° along the same direction as the strip, and a spray height of 150mm-200mm.

[0015] Furthermore, the concentration C of the alkali solution OH =k C OH This refers to the concentration of the alkali solution, where K is the neutralization coefficient. The concentration of the acid in the first section, The processing time for the first stage of acid solution, The concentration of the acid in the second stage, The second stage of acid treatment time, The concentration of the acid in the third stage, The third stage acid treatment time, L is the length of the alkali tank, and V is the belt speed.

[0016] Furthermore, the conductivity of the water washing section and the strip thickness after the pickling section are monitored in real time, and the neutralization coefficient K is adjusted according to the conductivity and the strip thickness.

[0017] The present invention has at least the following advantages or beneficial effects: The present invention uses a surface conditioning liquid to treat the surface of the INVAR strip first, which can reduce or avoid the occurrence of pitting corrosion, improve the removal efficiency of foreign matter on the surface of the INVAR strip, reduce the low defect rate, and improve the strong rust prevention capability. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a novel INVAR strip cleaning method proposed in this invention;

[0020] Figure 2 Image showing the cleaning effect of INVAR strip without surface conditioning solution treatment;

[0021] Figure 3 This is a diagram showing the cleaning effect of INVAR strip treated with surface conditioning solution, which is the first method used in this invention. Detailed Implementation

[0022] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will be combined with the accompanying drawings and specific implementations to make a clear and complete description of the technical solutions in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations.

[0023] It should be noted that similar reference numerals and letters refer to similar items throughout the accompanying drawings, and thus, once an item is defined in one drawing, it is not necessary to further define and explain it in subsequent drawings.

[0024] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0025] In addition, the terms "horizontal", "vertical" and the like do not mean that the components must be absolutely horizontal or vertical, but can be slightly inclined. For example, "horizontal" only means that its direction is relatively more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined.

[0026] In the description of the present application, it should also be noted that unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0027] The embodiment of the present application provides a kind of INVAR strip surface cleaning method, wherein the main component of INVAR strip is Fe, Ni, other components contain C, Cr, Mn, S, Si, INVAR strip surface foreign matter mainly has surface oxide, carbide, oil stain dirt, gel foreign matter, rust stain.The main components of surface oxide are FeO, Fe2O3, Fe3O4, NiO, Ni3O4 etc., the main components of surface carbide are C, O, Fe, Ni etc., the main components of surface oil stain dirt are C, O, P, N, Si etc., the main components of gel foreign matter are C, N, O etc., and the main components of rust mark are Fe, Ni, C, O etc.

[0028] The embodiment of the present application provides a kind of INVAR strip surface cleaning method, as shown in Figure 1 The embodiment of the present application provides a kind of INVAR strip surface cleaning method, as shown in

[0029] S2: the INVAR strip surface after cleaning in step S1 is treated using pickling section;

[0030] S3: the INVAR strip surface after treatment in step S2 is cleaned using alkaline cleaning section;

[0031] S4: the INVAR strip surface after treatment in step S3 is treated using water washing section and drying section.

[0032] The INVAR strip surface is first treated using surface conditioning liquid in step S1, because the INVAR metal strip surface oxide film is not dense, and the thickness is uneven, if directly using pickling, acid solution will preferentially penetrate the weak area of oxide film, easy to occur INVAR metal strip local overcorrosion, form pitting pit, cause the appearance of metal surface to be new abnormality.Therefore, first using surface conditioning liquid to remove oxide film, reduce or avoid pitting phenomenon to occur.As shown in Figure 2 The effect diagram of INVAR strip cleaning after using surface conditioning liquid to treat INVAR strip surface, INVAR strip surface after cleaning has pitting. Figure 3 The effect diagram of INVAR strip cleaning after using surface conditioning liquid to treat INVAR strip surface, INVAR strip surface after cleaning has pitting.

[0033] The surface conditioning liquid includes surfactant, acidic component, corrosion inhibitor and deionized water, the surfactant is sodium dodecyl sulfonate, the acidic component is composed of sulfamoyl acid, phosphoric acid and potassium acetate, and the corrosion inhibitor is benzotriazole.

[0034] By precisely designing the surface conditioning liquid formula, selecting different types and proportions of specific surfactants and acidic components, and utilizing the comprehensive effects of dissolution, complexation, wetting, penetration, dispersion, and suspension, the various different valence iron oxides on the metal surface can be effectively removed. The iron oxides are composed of Fe 2+ , Fe 3+ , and mixed valence states.

[0035] The surfactant sodium dodecyl sulfonate reduces surface tension, enhances wetting and penetration, and loosens the oxide. The concentration of the surfactant is in the range of 6%-8%, and the mass ratio of the surfactant to the acidic component is 1:1.5-1:2.0.

[0036] The sulfamoyl acid in the acidic component can quickly dissolve Fe2O3 (trivalent iron) to form a soluble iron sulfonate complex. The concentration of the sulfamoyl acid is in the range of 4%-6%, and the sulfamoyl acid accounts for 40% of the total amount of the acidic component.

[0037] The phosphoric acid in the acidic component can chelate Fe 2+ , Fe 3+ to generate a phosphoric iron passivation film that inhibits re-rusting and has a micro-roughening effect. The concentration of the phosphoric acid is in the range of 3%-5%, and the complexing ratio of the phosphoric acid to the sulfamoyl acid is 1:1.2-1:1.5.

[0038] The potassium acetate in the acidic component can buffer pH fluctuations, complex Fe 2+ , and prevent precipitation to improve the stability of the solution. The concentration of the potassium acetate is in the range of 2%-4%, and the potassium acetate accounts for 20% of the total amount of the acidic component.

[0039] The corrosion inhibitor benzotriazole can be adsorbed on the active sites of the metal to form a protective film. Due to the synergistic protection of Ni / Fe, the corrosion of the Invar metal substrate can be inhibited. The concentration is in the range of 0.8%-1.2%, and the molar ratio to the surfactant is 1:0.5-1:0.8. Ni / Fe synergistic protection refers to the possible joint action of nickel and iron on the metal surface with the corrosion inhibitor (benzotriazole) to form a more dense protective film. This protective film can effectively prevent the contact between corrosive media (such as acid, alkali, salt, etc.) and the metal substrate, thereby inhibiting the corrosion of the metal substrate.

[0040] In step S1, hot water is also used to clean the surface of the metal strip to remove residual surface conditioning materials and other foreign matter on the surface. In this case, the water is deionized water or pure water, and cleaning the surface of the metal strip with hot water can improve the cleaning efficiency.

[0041] In an optional embodiment, in step S2, the pickling section is composed of three pickling stages. By adjusting the acid concentration and composition of each pickling stage, impurities with different chemical stabilities can be dissolved step by step, thereby removing different types of surface impurities step by step.

[0042] The first pickling in the three-stage pickling is composed of 5%-8% glycolic acid and 0.5%-1% sodium gluconate, the temperature is 35-45°C, the process time is 90-110s, the spraying pressure is 0.2-0.3bar, the spraying angle is 15-20° along the direction of the strip, and the spraying height is 250-300mm. The first pickling adopts very low pressure to wet the surface of the metal strip to prevent splashing, and spreads the liquid film along the direction of the strip, and the high spraying height has a high drop to gently cover the metal surface. The first pickling mainly dissolves organic oil and dust, and can remove non-metallic adsorbents, and the surface roughness Ra of the strip surface does not change.

[0043] The direction of the strip refers to the running direction of the strip on the continuous production line, that is, the horizontal longitudinal motion direction from the inlet to the outlet; the direction along the strip refers to the same direction as the running direction of the strip (included angle 0°-45°); and the direction opposite to the strip refers to the opposite direction to the running direction of the strip (included angle 135°-180°).

[0044] The second pickling in the three-stage pickling is composed of 1.5%-2.5% sulfamic acid and 0.1%-0.5% polyaspartic acid, the temperature is 40-50°C, the process time is 60-80s, the spraying pressure is 0.8-1.0bar, the spraying angle is 60-75° along the direction opposite to the strip, and the spraying height is 100-150mm. The second pickling adopts medium pressure to strip the particles on the surface of the metal strip, and the opposite direction enhances the shear force, and the small spraying height can accurately impact the particles at a close distance. The complex removes the metal particles on the surface of the strip, mainly removes Fe oxide, Ni oxide and Cr oxide, and after the second pickling, the residual metal particles on the metal strip are ≤5 / cm2, and the surface roughness Ra of the strip is less than or equal to 0.005μm.

[0045] The third pickling in the three-stage pickling is composed of 0.8%-1.8% ammonium oxalate and 0.02%-0.05% fluorocarbon surfactant. The temperature is 30-40°C, the process time is 45-55s, the spraying pressure is 0.1-0.2bar, the spraying angle is 5-10° along the direction of the strip, and the spraying height is 300-350mm. The third pickling adopts ultra-low pressure to reduce residual adsorption, horizontal flow to prevent liquid drop accumulation, and the large spraying height can volatilize auxiliary at a long distance. This section adopts ion state residual desorption, and the surface energy of the strip can be reduced to as low as 30mN / m, and the surface roughness Ra of the strip is less than or equal to 0.02μm.

[0046] The step S2 includes cleaning the surface of the metal strip with cold water to remove residual acid and other foreign matters on the surface.

[0047] In the optional embodiment of the present case, the number of alkaline liquid stages in step S3 is not required, and only one alkaline washing stage or multiple alkaline washing stages can be selected for cleaning treatment. The present embodiment preferably comprises two alkaline washing stages, both of which mainly consist of sodium carbonate. In the first alkaline washing stage, the spraying pressure is 1.8-2.2 bar, the spraying angle is 60-70° along the reverse strip direction, the spraying height is 80-90 mm, the pH range of the first alkaline washing liquid is 9-10, and the temperature is 40-50°C. In the first alkaline washing stage, high pressure is used to ensure rapid neutralization of acid residues on the surface of the strip, a large angle is used to enhance the impact force, and a small spraying height is used to improve the reaction efficiency at close range.

[0048] In the second alkaline washing stage of the alkaline washing stage, the spraying pressure is 0.8-1.0 bar, the spraying angle is 30-40° along the forward strip direction, the spraying height is 150-200 mm, the pH range of the second alkaline washing liquid is 9-10, and the temperature is 40-50°C. In the second alkaline washing stage, a small angle is used to form a uniform liquid film, and a large spraying height is used to expand the coverage uniformity at a long distance.

[0049] wherein the concentration of the alkaline liquid in the alkaline washing stage is C OH =k wherein C OH is the concentration of the alkaline liquid, the unit is wt%, K is the neutralization coefficient, the concentration of the first-stage acid liquid, the unit is wt%, the treatment time of the first-stage acid liquid, the unit is s, the concentration of the second-stage acid liquid, the unit is wt%, the treatment time of the second-stage acid liquid, the unit is s, the concentration of the third-stage acid liquid, the unit is s, the treatment time of the third-stage acid liquid, the unit is s, L is the length of the alkaline liquid tank, the unit is m, and V is the metal strip speed, the unit is m / s.

[0050] In the cleaning process of the metal strip, the conductivity of the water washing stage is monitored in real time, and the thickness of the strip after the acid washing stage is completed. The neutralization coefficient K is adjusted according to the conductivity and the thickness of the strip.

[0051] Firstly, according to the thickness of the strip, the preliminary value range of the neutralization coefficient K can be determined. Specifically as follows:

[0052] For thin metal strips (thickness 0.01-0.05 mm), the K value should be controlled between 1.8-2.2. Thin strips require excessive neutralization to prevent acid residues, so a higher K value is selected.

[0053] For medium-thickness metal strips (thickness 0.05-0.1 mm), the K value should be controlled between 1.3-1.7. The medium-thickness strip has a relatively balanced requirement for neutralization, so the K value range is relatively narrow.

[0054] For thick material of metal strip (thickness > 0.1 mm): K value should be controlled between 0.9-1.2, thick material reacts slowly, need to extend the neutralization time rather than increase the concentration, so choose lower K value.

[0055] Secondly, according to the conductivity of the terminal water washing section, we can further adjust the K value to ensure that the acid residue is effectively controlled, while avoiding excessive neutralization that may damage the passivation film.

[0056] High conductivity (> 10 μS / cm), K value should be controlled at about 0.5, high conductivity indicates that there is more acid residue, which needs to increase the alkali concentration to neutralize the excess acid.

[0057] Low conductivity (< 2 μS / cm), K value should be controlled at about 0.3, low conductivity indicates that there is less acid residue, which should reduce the alkali concentration to avoid excessive neutralization.

[0058] Combining the thickness of the strip and the conductivity of the terminal water washing section, the neutralization coefficient K value can be adjusted comprehensively. For thin material, if the conductivity is high, the K value can be appropriately increased to ensure that the acid residue is fully neutralized; if the conductivity is low, the K value can be appropriately reduced to avoid excessive neutralization. For medium thickness strip, adjust the range of K value according to the conductivity to ensure the balance between neutralization effect and passivation film protection. For thick material, due to slow reaction, it should be mainly realized by extending the neutralization time, the adjustment of K value should be more cautious to avoid damage to the passivation film due to high alkali concentration.

[0059] In the implementation process, the conductivity of the terminal water washing section and the surface state of the strip should be continuously monitored, and the K value should be dynamically adjusted according to the actual situation. In addition, the corrosion resistance of the strip should be checked regularly to ensure the effectiveness and stability of the neutralization process. In summary, the neutralization coefficient K can be adjusted according to the thickness of the strip and the conductivity of the terminal water washing section to achieve the best neutralization effect and passivation film protection.

[0060] In step S4, the surface of the INVAR strip is treated by water washing section and drying section.

[0061] The water washing section in step S4 includes three sections, the first section uses hot water to wash the strip in turbulent flow, the water temperature is 50-60℃, high temperature improves the ion adsorption energy, turbulent flow can increase the shear force to strip the surface of the metal strip of large particle residue.

[0062] The second section of water washing uses hot water to ultrasonic clean the strip, the water temperature is 40-50℃, temperature above 40℃ can maintain the solubility of surfactants and other ingredients, ultrasonic cleaning can strip the surface of the metal strip of submicron particle residue.

[0063] The third section of water washing uses cold water to perform low negative pressure suction on the strip, and the vacuum degree is 60-85 kPa, and the vacuum negative pressure suction removes the liquid medicine and particle residues in the gap of the strip.

[0064] The drying section process is not limited further, and one drying process or a combination of multiple drying processes can be used to fully dry the surface of the metal strip, such as compressed drying clean gas air knife blowing, centrifugal spinning, infrared radiation drying, vacuum microwave drying, etc.

[0065] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for cleaning the surface of INVAR strip, characterized in that it comprises the steps of: S1: first cleaning the surface of the INVAR strip with a surface conditioning liquid; S2: treating the surface of the INVAR strip cleaned in step S1 with an acid pickling section; S3: treating the surface of the INVAR strip treated in step S2 with an alkaline cleaning section; S4: treating the surface of the INVAR strip treated in step S3 with a water cleaning section and a drying section; the surface conditioning liquid comprises a surfactant, an acidic component, a corrosion inhibitor, and deionized water, the surfactant is sodium dodecyl sulfonate, the acidic component is composed of sulfamoyl acid, phosphoric acid, and potassium acetate, and the corrosion inhibitor is benzotriazole. The ratio of the surfactant to the acidic component is 1:1.5-1:2.0, and the molar ratio of the surfactant to the corrosion inhibitor is 1:0.5-1:0.

8. The sulfamoyl acid accounts for 35%-45% of the total amount of the acidic component, the potassium acetate accounts for 15%-25% of the total amount of the acidic component, and the ratio of the phosphoric acid to the sulfamoyl acid is 1:1.2-1:1.

5. The concentration of the sodium dodecyl sulfonate is 6%-8%, the concentration of the sulfamoyl acid is 4%-6%, the concentration of the phosphoric acid is 3%-5%, the concentration of the potassium acetate is 2%-4%, and the concentration of the benzotriazole is 0.8-1.2%. The acid pickling section is composed of three acid pickling sections, the first acid pickling section is composed of 5%-8% glycolic acid and 0.5%-1% sodium gluconate, the second acid pickling section is composed of 1.5%-2.5% sulfamoyl acid and 0.1%-0.5% polyaspartic acid, and the third acid pickling section is composed of 0.8%-1.8% ammonium oxalate and 0.02%-0.05% fluorocarbon surfactant. The spraying pressure of the first acid pickling section is 0.2-0.3 bar, the spraying angle is 15º-20º along the strip direction, the spraying height is 250mm-300mm, the temperature is 35℃-45℃, and the process time is 90s-110s; the spraying pressure of the second acid pickling section is 0.8-1.0 bar, the spraying angle is 60º-75º along the reverse strip direction, the spraying height is 100mm-150mm, the temperature is 40℃-50℃, and the process time is 60s-80s; the spraying pressure of the third acid pickling section is 0.1-0.2 bar, the spraying angle is 5º-10º along the strip direction, the spraying height is 300mm-350mm, the temperature is 30℃-40℃, and the process time is 45s-55s.

2. A method of cleaning the surface of an INVAR strip as claimed in claim 1, characterized in that: The alkaline cleaning section is composed of two alkaline cleaning sections, the spraying pressure of the first alkaline cleaning section is 1.8-2.2 bar, the spraying angle is 60º-70º along the reverse strip direction, and the spraying height is 80mm-90mm; the spraying pressure of the second alkaline cleaning section is 0.8-1.0 bar, the spraying angle is 30º-40º along the strip direction, and the spraying height is 150mm-200mm.

3. A method of cleaning the surface of an INVAR strip as claimed in claim 1, characterized in that: ​ 4. A method of cleaning the surface of an INVAR strip as claimed in claim 1, characterized in that: ​ 5. A method of cleaning the surface of an INVAR strip as claimed in claim 1, characterized in that: ​ 6. A method of cleaning the surface of an INVAR strip as claimed in claim 5, characterized in that: ​ 7. A method of cleaning the surface of an INVAR strip as claimed in claim 5, characterized in that: ​ 8. A method of cleaning the surface of an INVAR strip as claimed in claim 5, characterized in that: alkali concentration C of the alkali cleaning section OH =k wherein C OH is the alkali concentration, K is the neutralization coefficient, the concentration of the first section of acid, the treatment time of the first section of acid, the concentration of the second section of acid, the treatment time of the second section of acid, the concentration of the third section of acid, the treatment time of the third section of acid, L is the length of the alkali tank, V is the strip speed.

9. A method of cleaning the surface of an INVAR strip as claimed in claim 8, characterized in that: The conductivity of the water washing section is monitored in real time, the strip thickness after the end of the acid washing section, the neutralization coefficient K is adjusted according to the conductivity and the strip thickness. The conductivity of the water washing section is monitored in real time, the strip thickness after the end of the acid washing section, the neutralization coefficient K is adjusted according to the conductivity and the strip thickness.

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